JPH03200237A - Electronic image pickup device - Google Patents

Abstract

PURPOSE:To accomplish high-speed consecutive photographing even in the case of using a TTL system optical finder by providing a photoelectric conversion surface where square picture elements are regularly arranged crosswise and which is nearly perpendicular to an optical axis and making the position of the photoelectric conversion surface satisfy a specified condition. CONSTITUTION:This device is constituted of a photographing lens 1, a thin translucent plate 2 obliquely crossed with the optical axis of the lens 1, and an electronic image pickup element having the photoelectric conversion surface 3 where the square picture elements are regularly arranged crosswise and which is nearly perpendicular to the optical axis 2. Supposing that a plane including the normal of the thin translucent plate 2 and the optical axis is taken as a meridian plane, the positions of a tangential image point and a sagettal image point on the optical axis with reference to an object point on the optical axis are taken as IM and IS, and the inside sizes of the meridian plane and the sagittal plane of the square picture element are taken as M and S respectively, the position I of the photoelectric conversion surface 3 satisfies any set of formulars I-IV. In the case that accumulated charges of plural adjacent picture elements are mixed to obtain a signal, the plural picture elements are integrated to be dealed as one picture element. Thus, the lowering of resolving power caused by astigmatic difference is kept to the minimum by making use of the characteristic of the image pickup element and the high-speed consecutive photographing is accomplished even in the case of using the TTL system optical finder.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、撮像光学系中に光軸に対して斜交された薄い
透明板又は半透明板を含んでいるカメラ等の電子撮像装
置に関するものである。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electronic imaging device such as a camera that includes a thin transparent plate or semi-transparent plate obliquely crossed with respect to the optical axis in an imaging optical system. It is something.

〔従来の技術〕[Conventional technology]

電子撮像素子を用いたカメラの最大の特徴の一つに、電
子撮像素子の撮像面が小さいことにより撮影レンズの変
倍比を大きくとれることが挙げられる。そのファインダ
ーには、電子ビュー式のものもあるが、「見え」などの
点で光学式のものも捨て難い。そして、変倍比の大きな
撮像光学系のためのファインダーは撮影範囲と観察範囲
とのズレの補正が容易であるため、技術的にはＴＴＬ方
式を用いるのが良い。そのため、撮像光学系から２　（
Ｍ＋Ｓ）　　　　　　　　２　（Ｍ＋Ｓ）ファインダー
側へミラー等を用いて光を導くことになるが、従来は撮
影の瞬間のみミラーが撮影光路外へ外れる所謂クイック
リターンミラーを用いていた。しかしながら、電子撮像
素子を用いたカメラのもう一つの特徴として、高速速写
があげられ、この場合前記クイックリターンミラーを用
いていたのではその作動速度が遅いため、甚だ具合が悪
い。従って、電子撮像素子を用いたカメラには、ハーフ
ミラ−を用いるのが良い。ハーフミラ−としては、反射
膜コート面を二つの硝子ブロックにてサンドウィッチに
したものや、硝子板に反射膜をコートしたもの（半透明
板）を用いることになるが、前者は偏光度が高いため、
測光の面で或は撮像の面で不都合を生じやすく、これを
緩和するために、反射率を極力低くするか又は反射面の
法線と光軸とのなす角を極力小さくして用いなくてはな
らない。従って、偏光度の低い後者を用いるのが良い。One of the greatest features of cameras using electronic image sensors is that the small imaging surface of the electronic image sensor allows for a large zoom ratio of the photographic lens. Some of these finders are electronic view types, but optical ones are also difficult to throw away due to their visibility. Technically, it is better to use the TTL method for a finder for an imaging optical system with a large zoom ratio because it is easy to correct the deviation between the photographing range and the observation range. Therefore, 2 (
M+S) 2 (M+S) Light is guided to the finder side using a mirror or the like, but conventionally a so-called quick return mirror has been used in which the mirror moves out of the photographing optical path only at the moment of photographing. However, another feature of cameras using electronic image pickup devices is high-speed snapshots, and in this case, using the quick return mirror would be extremely inconvenient due to its slow operating speed. Therefore, it is preferable to use a half mirror in a camera using an electronic image sensor. Half mirrors can be made by sandwiching the reflective film-coated surface between two glass blocks, or by coating a glass plate with a reflective film (semi-transparent plate), but the former has a high degree of polarization. ,
Inconveniences tend to occur in terms of photometry or imaging, and in order to alleviate this problem, it is necessary to reduce the reflectance as much as possible or to minimize the angle between the normal to the reflective surface and the optical axis. Must not be. Therefore, it is better to use the latter, which has a lower degree of polarization.

又、一部の光が全反射するようにすれば、薄いハーフミ
ラ−の代わりに薄い透明板を用いることもできる。Further, if a part of the light is totally reflected, a thin transparent plate can be used instead of a thin half mirror.

〔発明が解決しようとする課題〕[Problem to be solved by the invention]

しかしながら、それらの場合、透過側に得られる像には
非点隔差が発生する。即ち、上記反射面の法線と前記光
軸とを含む平面（子午面）に含まれる方向の成分とそれ
に垂直な面（球欠面）に含まれる方向の成分との結像点
にある一定のズレを生ずる。この差は前記ハーフミラ−
又は透明板の厚みにほぼ比例するのでそれらの材料に極
力薄い硝子板又は樹脂板等を用いることが前提となるが
、前記非点隔差は要求解像力を考えた場合無視出来なく
なる場合がある。However, in those cases, an astigmatism difference occurs in the image obtained on the transmission side. That is, a constant value at the imaging point of the component in the direction included in the plane (meridional plane) containing the normal line of the reflecting surface and the optical axis and the component in the direction included in the plane perpendicular to it (the spherical plane). This will cause a misalignment. This difference is due to the half mirror
Alternatively, since it is approximately proportional to the thickness of the transparent plate, it is assumed that a glass plate or a resin plate as thin as possible is used as the material, but when considering the required resolution, the astigmatism difference may not be negligible.

本発明は、上記問題点に鑑み、撮像光学系内に薄いハー
フミラ−（半透明板）又は透明板を入れたために発生す
る非点隔差による解像力の低下を撮像素子の特性を生か
すことで最小限に留めることができ、その結果高変倍撮
像光学系のためにＴＴＬ式光学ファインダーを用いても
高速速写（秒２０コマ程度）が可能になるようにした電
子撮像装置を提供することを目的としている。In view of the above-mentioned problems, the present invention minimizes the reduction in resolution due to the astigmatic difference caused by inserting a thin half mirror (semi-transparent plate) or transparent plate in the imaging optical system by making use of the characteristics of the imaging element. The purpose of the present invention is to provide an electronic imaging device that enables high-speed shooting (approximately 20 frames per second) even when using a TTL optical viewfinder due to its high zoom ratio imaging optical system. There is.

〔課題を解決するための手段及び作用〕本発明による電
子撮像装置は、物体側から順に、撮影レンズと、該撮影
レンズの光軸に対し斜交する薄い半透明板又は透明板と
、方形の画素が縦横に規則正しく配列された前記光軸と
ほぼ垂直な光電変換面を有する電子撮像装置とが配置さ
れて成る撮像光学系を備えた電子撮像装置において、前
記薄い半透明板又は透明板の法線と前記光軸とを含む平
面を子午面とし、前記光軸上のある物点に関する前記光
軸上の子午像点位置及び球欠像点位置を夫々ＩＭ及びＩ
、とし、前記方形の画素の子午面内寸法及び球欠面寸法
を夫々Ｍ及びＳとした時、前記光電変換面の位置Ｉが以
下の条件式（１）、　（２）又は（３）、　＋４）の何
れかの組を満足することを特徴としている。[Means and effects for solving the problems] The electronic imaging device according to the present invention includes, in order from the object side, a photographic lens, a thin translucent plate or transparent plate obliquely intersecting the optical axis of the photographic lens, and a rectangular shape. In an electronic imaging device equipped with an imaging optical system including an electronic imaging device having a photoelectric conversion surface substantially perpendicular to the optical axis in which pixels are regularly arranged vertically and horizontally, the thin semi-transparent plate or transparent plate method is provided. A plane including the line and the optical axis is defined as a meridional plane, and the meridional image point position and the spherical defective image point position on the optical axis with respect to a certain object point on the optical axis are respectively IM and I.
, and when the meridional plane dimension and the spherical dimension of the rectangular pixel are M and S, respectively, the position I of the photoelectric conversion surface satisfies the following conditional expressions (1), (2), or (3), +4).

Ｌ２１　　Ｌ＞Ｌ １４］１１＜１１ 以下、これについて詳細に説明する。L21 L>L 14] 11<11 This will be explained in detail below.

第１図は本発明による電子撮像装置の撮影光学系の概念
図であって、これは物体側から順に、撮影レンズ１と、
その光軸に対し斜交する薄いノ翫−フミラー（半透明板
）２と、方形の画素が縦横に規則正しく配列された前記
光軸とほぼ垂直な光電変換面３を有する電子撮像素子と
からなり、ノ＼−フミラー２を反射板としてファインダ
ー側に光を導いている。FIG. 1 is a conceptual diagram of a photographing optical system of an electronic imaging device according to the present invention, which shows, in order from the object side, a photographing lens 1,
It consists of a thin mirror (semi-transparent plate) 2 that is oblique to the optical axis, and an electronic image sensor that has a photoelectric conversion surface 3 that is substantially perpendicular to the optical axis and has rectangular pixels regularly arranged vertically and horizontally. The light is guided to the finder side using the nof mirror 2 as a reflector.

光軸上のある物点に関し、透過側では前記ノへ−フミラ
ー２の法線と前記光軸とを含む平面（子午面）に含まれ
る方向の成分の結像点位置（子午像点位置ＩＭ）と、そ
れに垂直な面（球欠面）に含まれる方向の成分との結像
点位置（球欠像点位置ＩＳ）にある一定のズレ即ち非点
隔差が発生する。Regarding a certain object point on the optical axis, on the transmission side, the imaging point position (meridian image point position IM ) and a component in a direction included in a plane perpendicular to it (spherical defective surface), a certain deviation, that is, an astigmatism difference occurs in the imaging point position (spherical defective image point position IS).

前記撮影レンズが無収差であれば、物点像はこの二つの
結像点位置の中点においてほぼ円となるが、それ以外例
えば子午像点位置ＩＭＩ球欠像点位置Ｉ５では第２図（
Ａ）、（Ｂ）に示した如（はぼ楕円となる。又、子午像
点位置ＩＭと球欠像点位置ＩＳのＹ、　Ｘの内分点では
ほぼ長辺：短辺＝Ｙ　：　Ｘ　（Ｙ＞Ｘ）の楕円になる
。そして、電子撮像素子（ＣＣＤなど）の光電変換面の
方形の画素の長辺と短辺の比と前記楕円の長辺と短辺の
比がほぼ一致すれば、撮像素子の画素数にて決まる諸性
能（解像度など）を無駄な（発揮させることができる。If the photographing lens has no aberration, the object point image will be approximately circular at the midpoint of these two image forming point positions, but otherwise, for example, at the meridian image point position IMI and the spherical defective image point position I5, as shown in FIG.
As shown in A) and (B), it becomes an ellipse.Also, at the internal division point of Y and X of the meridian image point position IM and the spherical defective image point position IS, the long side: short side = Y: X It becomes an ellipse with (Y > For example, various performances (resolution, etc.) determined by the number of pixels of the image sensor can be utilized in a wasteful manner.

即ち、第３図に示した如く画素の子午面上の寸法をＭ、
球欠面上の方向の寸法をＳとすると、Ｙ＝Ｍ、Ｘ＝Ｓと
なるので、子午像点位置１１、Ｌと球欠像点位置Ｉ、と
のＭｉｓの内分点位置面３を光軸に対しほぼ垂直に配置
すれば、本光学系による点像形状が第４図に示した如く
画素形状と近くなり、縦横夫々の解像度を共に高くする
ことができる。That is, as shown in FIG. 3, the dimensions of the pixel on the meridian plane are M,
If the dimension in the direction on the sphere defective surface is S, then Y=M and X=S, so the internal division point position plane 3 of Mis between the meridian image point position 11, L and the sphere defective image point position I is If arranged substantially perpendicular to the optical axis, the point image shape of this optical system becomes close to the pixel shape as shown in FIG. 4, and the resolution in both the vertical and horizontal directions can be increased.

但し、第４図の点像の形状及び寸法は画素の寸法を第３
図に示した如くｘ方向９μｍ、ｙ方向１８μｍとした時
の像面位置Ｉ即ち ９＋１８　　　　　　　　　　３ におけるものである。その点をＩ　ＢＥＳＴとする。However, the shape and dimensions of the point image in Figure 4 are based on the pixel dimensions
As shown in the figure, this is at the image plane position I, that is, 9+18 3 when the distance is 9 μm in the x direction and 18 μm in the y direction. Set that point as I BEST.

ここで、画素の子午面上での寸法をｍｌ、球欠面上での
寸法を８１とし、子午像点位置■８と球欠像点位置■８
とをｍ２　ｄｓｔに内分する点に光電変換面３を持って
きたとし、点像の長辺と短辺を夫々ｍ　ｔ　＋　　８２
　とする。Here, the dimension of the pixel on the meridian plane is ml, the dimension on the spherical defect surface is 81, and the meridian image point position ■8 and the spherical defect point position ■8
Assume that the photoelectric conversion surface 3 is brought to a point that internally divides .
shall be.

前記ハーフミラ−２は薄くするにこしたことはないが、
強度の点でできるだけ厚くしなければならない。そこで
、点像が方形の画素に丁度内接する程度に即ちｍ＊　ｋ
ｒｒｌ＋　＋　　Ｓ　ｔ　＃Ｓ　＋　となるようハーフ
ミラ−２の厚さｔを厚くする（１＝１．、、）すると、
前記ハーフミラ−２を含む撮影光学系の解像力は、子午
方向２球欠方向夫々のナイキスト周波数となるので問題
はない。ここで光電変換面３の位置を前記位置より例え
ば子午像点位置１Ｍ側へずらすと、子午方向の撮像光学
系の解像流量行くは向上するが、モアレ縞防止フィルタ
ー等により結局解像力はたかだかナイキスト周波数どま
りである。一方、球欠方向についてはボケが広がるため
、その方向の解像力はナイキスト周波数以下となってし
まう。しかしながら、実用的には、多少のズレは許容さ
れて良いであろう。特に、前記ハーフミラ−２の厚みｔ
が上述のようにｔ　ｆｆ１Ｘ以下の場合があてはまる。Although there is no need to make the half mirror 2 thinner,
It must be as thick as possible in terms of strength. Therefore, to the extent that the point image is exactly inscribed in a square pixel, that is, m* k
When the thickness t of the half mirror 2 is increased so that rrl+ + S t #S + (1=1.,),
The resolving power of the photographing optical system including the half mirror 2 is at the Nyquist frequency in each of the two meridional directions, so there is no problem. If the position of the photoelectric conversion surface 3 is shifted from the above-mentioned position, for example, toward the meridian point position 1M, the resolution flow rate of the imaging optical system in the meridian direction will improve, but in the end, the resolving power will be reduced to Nyquist due to the moiré fringe prevention filter, etc. The frequency is limited. On the other hand, since the blur spreads in the direction where the ball is missing, the resolution in that direction becomes less than the Nyquist frequency. However, in practical terms, some deviation may be acceptable. In particular, the thickness t of the half mirror 2
This applies to the case where t ff1X or less as described above.

その範囲は、■、とＩ　ＢＥＳＴの中点からＩ　ＢＥＳ
ＴとＩＭの中点までとして良い。The range is from the midpoint of ■ and I BEST to I BES
It may be up to the midpoint between T and IM.

■、とＩ。５Ｔの中点は、 である。又、■、。、ＴとＩＭの中点は、である。従っ
て、画質上効率が良（なる像面位置■は １＋ｓ） ｔ（Ｍ＋Ｓ） の範囲に入れることが望ましいことになる。但し、■□
＞　Ｉ　ｓ　　　　　　　　　　　　　・・・・（２）
である。又、逆に １ＭくＩ３　　　　　　　　　　・・・・（４）であれ
ば、画質上効率が良（なる像面位置１は・・・・（３） の範囲に入れることが望ましいことになる。この範囲を
外れると、点像の子午方向９球欠方向の何れかにおいて
ナイキスト周波数に比べて太き（下廻る解像力となり、
好ましくない。又、前記ハーフミラ−２が厚すぎること
によっても解像力がナイキスト周波数を太き（下廻って
しまうことになるので、 ｔ　＜　０．２　Ｆ　Ｎｏ　　　　　　　　　　”ｆ５
）を満足するようにした方が良い。但し、ＦＮＯは撮影
レンズｌのＦナンバーである。もし、ハーフミラ−２の
厚さｔが０．２　Ｆ　Ｎｏを下廻る厚みになると、非点
隔差が拡がり、子午方向９球欠方向の何れか・・・・（
１） 又は両方の解像力がナイキスト周波数に比べて著しく低
くなる。■, and I. The midpoint of 5T is . Also, ■. , the midpoint between T and IM is . Therefore, it is desirable to set it in the range of t(M+S) which is efficient in terms of image quality (the image plane position (i) is 1+s). However, ■□
＞Is・・・(2)
It is. On the other hand, if 1M x I3...(4), it is desirable to have the image plane position 1 in the range of (3), which is efficient in terms of image quality.This range If it deviates from the point image, the resolution becomes thicker (below) than the Nyquist frequency in any of the 9 meridional directions of the point image,
Undesirable. Also, if the half mirror 2 is too thick, the resolving power will become thicker (below the Nyquist frequency), so t < 0.2 F No "f5
) should be satisfied. However, FNO is the F number of the photographing lens l. If the thickness t of the half mirror 2 becomes less than 0.2 F No., the astigmatism difference will increase, and it will be either in the meridian direction or in the 9-pitch direction... (
1) Or the resolution of both becomes significantly lower than the Nyquist frequency.

〔実施例〕〔Example〕

以下、図示した一実施例に基づき本発明の詳細な説明す
る。Hereinafter, the present invention will be described in detail based on an illustrated embodiment.

第５図は本実施例の撮影光学系を示しており、そのデー
タは以下に示す通りである。FIG. 5 shows the photographing optical system of this embodiment, and the data thereof are as shown below.

ｒ　＋”５８．７０６０ ｄ　＋＝１．６０００　　　ｎ　ｌ＝１．８４６６６　
　　！／　、＝２３．７８ｒ　ｚ＝３２．７９４０ ｄ　、＝０．０８００ ｒ　　３二３４．０１７０ ｄ３”３．６０００　　　ｎ　＊１．６０３１１　　　
νｔ”６０．７０ｒ　４＝−２９６，６３１０ ｄ　４＝０．１５００ ｒ　ａ：２７．３９５０ ｄ　ｓ＝２．９０００　　　ｎ　ｚｌ、　６９６８ＯＬ
’　３”５５．５２ｒ　、＝１２６．２９６０ ｄ　６＝１３．８５７　（可変） ｒ　？−９４，２８１０ ｄ　、＝０．９０００ ｒ　ｓ＝９．３５８０ ｄ　、＝２．５０００ ｒ　５＝−１３，１８４０ ｄ　、＝０．９０００ ｒ　＋ｏ：１３．１８４０ ｄ　、　、＝２．２０００ ｒ　、、＝−９３，３３５０ ｄ　ＩＩ・０．６００（可変） ｒ　ｌ！”４７．８’７９０ ｄｌ。＝１．６０００ ｒ　＋３＝−９８，２０２０ ｄ、、＝１．３００　（可変） ｒｚ・ｏＯ（絞り） ｄ　、　、　＝１．６０００ ｒｌ、＝１３．８６４０ ｄ　、　、　＝２．８０００ ｒ　、、＝−６８，４９７０ ｄ　、、＝０．４６００ ｒ　、、＝−１３，７８００ ｎ　、＝１．７０１５４ ｎ　ｙ４．８３４００ ｎ　ｅ４．８４６６６ ｎ　ｓ”１．７４３２０ ｎ　４＝１．８３４００ ν４　＝３７．１６ シ、　　＝４９．３１ ν、　　＝２３．７８ ν、　　＝３７．１６ シｓ　　＝４１．２１ ｄ　、　、　＝６．００００ ｒ　＋　１”２０．９１７０ ｄ　　Ｉに０．３８０Ｏ ｒ　、、＝５４．９３５０ ｄ　、　、　＝２．８０００ ｒ　、。＝−１４，９３５０ ｄ　＋−＝０．１５００ ｒ　２１：３１．２９３０ ｄ　、　、　＝２．５００Ｏ ｒ　＋＋”−３１，２９３０ ａ　２．＝ｔ３．１５００ １１ ｄ、、＝１．００００ ｒ　２．＝　■ ｄ　ｌ　、　＝４．８０００ ｒ　　＋ｓ”　　″ ｄ　２．＝１．０ＯＯＯ ｒ　　ｒｈ：　″ ｎ　ｉ４．８０５１８ ｎ　、　。＝１．６９６８０ ｎ　　、＝１．６９６８０ ｎ　、２＝１．５１６３３ ｎ　１．＝１．５４７７１ ν、　　＝２５．４３ ν ＝５５．５２ ν ＝５５．５２ シ、、＝６４．１５ ν、　３＝６２．８３ ｄ　、　、　＝０．７０００ ｎ　、、＝１．５１６３３ ν、　、＝６４．１５ ｒ　！＋：　″ ｄ　２　？　”０．３１００ ｒ　２＠：　″ ｄ　ｓｓ”０．６０００　　　ｎ　ｌ５＝１．４８７４
９　　　　Ｌ）＋＋”７０．２０ｒ２．＝ｏ。r +”58.7060 d +=1.6000 n l=1.84666
! / , =23.78r z=32.7940 d , =0.0800 r 32 34.0170 d3”3.6000 n *1.60311
νt"60.70r 4=-296,6310 d4=0.1500 r a:27.3950 ds=2.9000 n zl, 6968OL
'3"55.52r , = 126.2960 d 6 = 13.857 (variable) r ? -94,2810 d , = 0.9000 r s = 9.3580 d , = 2.5000 r 5 = -13, 1840 d , = 0.9000 r + o: 13.1840 d , , = 2.2000 r , , = -93,3350 d II・0.600 (variable) r l!”47.8'790 dl. =1.6000 r +3=-98,2020 d,, =1.300 (variable) rz・oO (aperture) d, , =1.6000 rl, =13.8640 d, , =2.8000 r,, =-68,4970 d,,=0.4600 r,,=-13,7800 n,=1.70154 ny4.83400 n e4.84666 ns”1.74320 n 4=1.83400 ν4 =37. 16 si, =49.31 ν, =23.78 ν, =37.16 sis =41.21 d, , =6.0000 r + 1”20.9170 d I to 0.380O r, ,=54 .9350 d, , =2.8000 r,. =-14,9350 d +-=0.1500 r 21:31.2930 d, , =2.500O r ++"-31,2930 a 2.=t3.1500 11 d,, =1.0000 r 2. = ■ d l , =4.8000 r +s” d 2. = 1.0OOO r rh: ” n i4.80518 n , . =1.69680 n , =1.69680 n , 2=1.51633 n 1. =1.54771 ν, =25.43 ν =55.52 ν =55.52 ci,, =64.15 ν, 3=62.83 d, , =0.7000 n,, =1.51633 ν, ,=64.15 r! +: ″ d 2 ? ”0.3100 r 2 @: ″ d ss ”0.6000 n l5=1.4874
9 L)++”70.20r2.=o.

ｆ＝２６．１４７１０　　、　　　　ＩＭ−Ｈ＝４．２
００００゜ＦＮＯ＝２．７１３　　　、　　　　ｔ＝０
．１５ｍｍθ＝４５＠ 但し、ｒｌは各面の曲率半径、ｄｌは面間隔、ｎｌは屈
折率、ν；はアツベ数である。又、ｆは全系の焦点距離
、ＩＭ−Ｈは像高、ＦＮＯは有効Ｆナンバー　ｔはハー
フミラ−２の厚さ、θはハーフミラ−２の傾きである。f=26.14710, IM-H=4.2
0000°FNO=2.713, t=0
．． 15mmθ=45@ However, rl is the radius of curvature of each surface, dl is the spacing between surfaces, nl is the refractive index, and ν; is the Abbe number. Further, f is the focal length of the entire system, IM-H is the image height, FNO is the effective F number, t is the thickness of the half mirror 2, and θ is the inclination of the half mirror 2.

第６図は本実施例のＭ−Ｄ特性（ＭＴＦと光軸上のデフ
ォーカス量との関係）即ち非点隔差の様子を示す図であ
って、実線は球欠方向の特性を点線は子午方向の特性を
夫々示している。FIG. 6 is a diagram showing the MD characteristic (relationship between MTF and the amount of defocus on the optical axis), that is, the astigmatism difference of this example, where the solid line indicates the characteristic in the direction of the spherical defect, and the dotted line indicates the meridian direction. The characteristics of each direction are shown.

この図によれば、曲面中心部においても子午像点と球欠
像点とが分離する所謂非点隔差が発生している（Ｍ−Ｄ
カーブのピーク位置に０．０５　ｍｍ程の隔差が出てい
る。）様子がわかる。点像は子午像点位置■３では球欠
方向が長辺となる楕円に近い形状となり、球欠像点位置
■５では子午方向が長辺となる楕円に近い形状となる（
第２図参照）。According to this figure, a so-called astigmatism difference occurs in which the meridian point and the spherical defect point are separated even at the center of the curved surface (M-D
There is a difference of about 0.05 mm between the peak positions of the curves. ) I can see what's going on. At meridian image point position ■3, the point image has a shape close to an ellipse with the long side in the direction of the spherical defect, and at point image point position ■5, it has a shape close to an ellipse with the long side in the meridian direction (
(See Figure 2).

更に、両像点間の中点近傍にてほぼ真円になる。Furthermore, it becomes almost a perfect circle near the midpoint between both image points.

そして、電子撮像素子の光電変換面の画素がＭ×Ｓの寸
法の方形だとし、その−辺（Ｍ）が子午方向に一致して
いるとすると、 Ｍ＋Ｓ なる位置では、子午方向寸法；球欠方向寸法−Ｍ：Ｓと
なる楕円に近い形状となり、画素と相似する形に近くな
り、解像力の点から効率が良くなる。Assuming that the pixels on the photoelectric conversion surface of the electronic image sensor are rectangular with dimensions M x S, and the - side (M) coincides with the meridian direction, at a position where M + S, the meridional dimension; The shape is close to an ellipse with the directional dimension -M:S, and is close to a shape similar to a pixel, which improves efficiency in terms of resolution.

尚、上記実施例では、電子撮像素子の画素の長辺が子午
方向、短辺が球欠方向である場合について説明している
が、逆に画素の長辺が球欠方向、短辺が子午方向である
場合にも上記条件式（１）、　（２）又は（３）、　（
４）が当てはまることは言うまでもない。In the above embodiment, the long side of the pixel of the electronic image sensor is in the meridian direction and the short side is in the spherical direction, but conversely, the long side of the pixel is in the spherical direction and the short side is in the meridian direction. The above conditional expressions (1), (2) or (3), (
It goes without saying that 4) applies.

〔発明の効果〕〔Effect of the invention〕

上述の如く、本発明による電子撮像装置は、撮像光学系
内に薄いハーフミラ−（半透明板）又は透明板を入れた
ために発生する非点隔差による解像力の低下を撮像素子
の特性を生かすことで最小限に留めることができ、その
結果高変倍撮像光学系のためにＴＴＬ式光学ファインダ
ーを用いても高速連写（秒２０コマ程度）が可能になる
という実用上重要な利点を有している。As described above, the electronic imaging device according to the present invention utilizes the characteristics of the imaging element to overcome the reduction in resolution due to the astigmatism difference that occurs due to the inclusion of a thin half mirror (semi-transparent plate) or transparent plate in the imaging optical system. This has the important practical advantage of allowing high-speed continuous shooting (approximately 20 frames per second) even when using a TTL optical viewfinder due to the high zoom ratio imaging optical system. There is.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明による電子撮像装置の撮影光学系の概念
図、第２図（Ａ）及び（Ｂ）は夫々子午像点位置及び球
欠像点位置における点像形状を示す図、第３図は電子撮
像素子の画素の形状を示す図、第４図は子午像点位置と
球欠像点位置との内分点位置における点像形状を示す図
、第５図は一実施例の撮影光学系を示す図、第６図は上
記実施例のＭ−Ｄ特性を示す図である。 ｌ・・・・撮影レンズ、２・・・・ハーフミラ−３・・
第１図 （Ａ）　　第２図 （Ｂ） ＋　１Ｊ／Ｊ　ｌ−（ｂ） 手続補正書（自発）FIG. 1 is a conceptual diagram of the imaging optical system of the electronic imaging device according to the present invention, FIGS. 2(A) and 2(B) are diagrams showing point image shapes at the meridian image point position and the spherical defect point position, respectively. The figure shows the shape of a pixel of an electronic image sensor, FIG. 4 shows the point image shape at the internally divided point position between the meridian image point position and the spherical defect point position, and FIG. 5 shows the photographing of one example. FIG. 6, which is a diagram showing the optical system, is a diagram showing the MD characteristics of the above embodiment. l...Photographing lens, 2...Half mirror 3...
Figure 1 (A) Figure 2 (B) + 1J/J l-(b) Procedural amendment (voluntary)

Claims (1)

【特許請求の範囲】 物体側から順に、撮影レンズと、該撮影レンズの光軸に
対し斜交する薄い半透明板又は透明板と、方形の画素が
縦横に規則正しく配列された前記光軸とほぼ垂直な光電
変換面を有する電子撮像素子とが配置されて成る撮像光
学系を備えた電子撮像装置において、 前記薄い半透明板又は透明板の法線と前記光軸とを含む
平面を子午面とし、前記光軸上のある物点に関する前記
光軸上の子午像点位置及び球欠像点位置を夫々Ｉ＿Ｍ及
びＩ＿Ｓとし、前記方形の画素の子午面内寸法及び球欠
面内寸法を夫々Ｍ及びＳとした時、前記光電変換面の位
置Ｉが以下の条件式（１）、（２）又は（３）、（４）
の何れかの組を満足することを特徴とする電子撮像装置
。 （１）［（２Ｍ＋Ｓ）Ｉ＿Ｓ＋ＳＩ＿Ｍ］／［２（Ｍ＋
Ｓ）］＜Ｉ＜［ＭＩ＿Ｓ＋（Ｍ＋２Ｓ）Ｉ＿Ｍ］／［２
（Ｍ＋Ｓ）］ （２）Ｉ＿Ｍ＞Ｉ＿Ｓ （３）［（２Ｍ＋Ｓ）Ｉ＿Ｓ＋ＳＩ＿Ｍ］／［２（Ｍ＋
Ｓ）］＞Ｉ＞［ＭＩ＿Ｓ＋（Ｍ＋２Ｓ）Ｉ＿Ｍ］／［２
（Ｍ＋Ｓ）］ （４）Ｉ＿Ｍ＜Ｉ＿Ｓ[Claims] In order from the object side, a photographic lens, a thin semi-transparent plate or transparent plate obliquely intersecting the optical axis of the photographic lens, and a lens approximately parallel to the optical axis in which rectangular pixels are regularly arranged vertically and horizontally. In an electronic imaging device equipped with an imaging optical system in which an electronic imaging element having a vertical photoelectric conversion surface is disposed, a plane including a normal line of the thin semi-transparent plate or transparent plate and the optical axis is defined as a meridian plane. , the meridional image point position and the spherical defective image point position on the optical axis with respect to a certain object point on the optical axis are respectively I_M and I_S, and the meridional plane dimension and the spherical defective dimension of the square pixel are respectively M and S, the position I of the photoelectric conversion surface satisfies the following conditional expressions (1), (2), or (3), (4)
An electronic imaging device that satisfies any one of the following. (1) [(2M+S)I_S+SI_M]/[2(M+
S)]<I<[MI_S+(M+2S)I_M]/[2
(M+S)] (2) I_M>I_S (3) [(2M+S)I_S+SI_M]/[2(M+
S)]>I>[MI_S+(M+2S)I_M]/[2
(M+S)] (4) I_M<I_S